TriglyAPCI

TriglyAPCI overview

TriglyAPCI is a tool for interpreting atmospheric pressure chemical ionization (APCI) mass spectra of triacylglycerols (TAGs).
It uses diacylglycerol fragments and molecular adducts for determining the structure. TriglyAPCI can process spectra of pure
compounds as well as mixtures and incomplete spectra lacking one of the diagnostic ions. If automatic data import is performed,
ion intensities of the fragments can be used to estimate TAG regiochemistry.

Triacylglycerols are among the most abundant lipids in nature. Their analysis is of great importance in food industry as well as in life science research.
They are triesters of glycerol, and each of the three positions in molecule may be occupied by different fatty acid. Not considering enantiomers, (N3+N2)/2
molecular species theoretically exist for N fatty acids. Natural TAGs are usually complex mixtures with tens to hundreds of isomers. HPLC/APCI-MS is a well-established method
for analyzing TAG mixtures. Mass spectra in the positive ion mode show primarily molecular adduct(s) [M+H]+, [M+NH4]+ etc. and diacylglycerol
fragment(s) [M+H-RiCOOH]+. Interpretation of the spectra is usually straightforward, consisting in the determination of fatty acid neutral losses. However,
it is time consuming especially in case of mixture analysis. Data interpretation usually requires more time than the sample analysis itself. Therefore, TriglyAPCI is
being developed to speed up interpretation and preclude possible mistakes.

TriglyAPCI is as a stand-alone Windows™ application developed in Visual Basic 6.0.environment. It uses Clipboard for spectra import. The current version supports ThermoFisher
Scientific Xcalibur datasystems and new version for Bruker DataAnalysis is being developed.

In the manual mode, fragments and molecular adducts are typed in the boxes in the left part of the main window, each ion on the separate line. After clicking "Manual"
button, the program lists all possible triacylglycerols. Limits for calculation (maximum number of double bonds, possible adduct species, mass tolerance etc.) are set in the
"Settings" window. After clicking on particular triacylglycerol in the "Suggestions" box, a short info is displayed in the right section of the main screen.
All expected diacylglycerol fragments and molecular adducts are listed together with chemical formula and equivalent carbon number (ECN). There are three search modes that
can be selected in the "Congruity" field. In the basic regime (Full-ALL) the software calculates triacylglycerols which are fully explained by the observed ions.
It means that all expected fragments and at least one molecular ion must be present in the spectrum for successful interpretation. Alternatively, TriglyAPCI can work with
incomplete set of ions, where either one fragment (Partial-2F/M) or molecular adduct (Partial-3F) is missing. Partial search modes are useful for processing spectra of low
abundant triacylglycerols with ion intensities close to background ions.

In the automatic mode, spectrum must be first exported from a datasystem to Clipboard. In Xcalibur, right mouse click in the spectrum window shows a dialog with "Export"
command. After selecting "Export (Exact mass)" the spectrum is placed to Clipboard. In TriglyAPCI, "Xcalibur Import" is clicked and the ions are automatically
loaded. Automatic mode is more convenient. Ion intensities are imported together with ion masses, which allows assignment to individual fatty acids to sn-2 or sn-1/3 position.

TriglyAPCI contain a tool for prediction of all triacylglycerol spectrum ions, including monoacylglycerol and acyl fragments.